In general, an excavation status monitoring system for a tunneling machine that detects a sound wave is known. Such an excavation status monitoring system for a tunneling machine is disclosed in Japanese Patent No. 3275085, for example.
In Japanese Patent No. 3275085, there is disclosed an excavation status monitoring system for a tunneling machine including an acoustic wave sensor mounted on a bulkhead of a rear portion of a closed chamber on the rear side of a cutter head (cutter face) and a speaker that outputs sound on the basis of a sound wave (signal) detected by the acoustic wave sensor. In this excavation status monitoring system for a tunneling machine, the acoustic wave sensor mounted on the bulkhead of the rear portion of the closed chamber on the back of the cutter head detects sound of ground excavation by the cutter head and outputs the detection signal as sound by the speaker, whereby an operator can perceive an excavation status aurally.